1. Field of the Invention
The present invention relates to a glass antenna for an automobile which is suitable for receiving signals in an FM broadcast band (76 to 90 MHZ) or a frequency band region having a higher frequency than the FM broadcast band.
2. Related Art
FIG. 2 shows a conventional glass antenna for an automobile adapted to receive signals in an FM broadcast band or a frequency band region having a higher frequency than the FM broadcast band in which an electric heating type defogger comprising heater strips 2 and bus bars 5a, 5b is provided in a rear window glass sheet 1 of an automobile, and an antenna conductor 14 is provided in a space above the defogger 3 in the rear window glass sheet 1.
The length of the antenna conductor 14 for receiving signals in the FM broadcast band is different from the length of the antenna conductor 14 for receiving signals in a higher frequency band than the FM broadcast band, and the length of the antenna conductor 14 for receiving signals in a higher frequency band than the FM broadcast band is short. Received signals induced in the antenna conductor 14 are supplied to a receiver 20 via a power feeding point 14a and a cable 25. A direct current is fed from a direct current power source 10 to the defogger 3.
In this conventional example, there is a problem that sensitivity to signals is insufficient even when signals in the FM broadcast band or a higher frequency band region than the FM are received. It is an object of the present invention to provide a glass antenna for an automobile which can eliminate the disadvantage of the conventional technique that sensitivity to signals is insufficient.
In accordance with the present invention, there is provided a glass antenna for an automobile in which an electric heating type defogger having a large number of heater strips and a plurality of bus bars, and an antenna conductor, are provided on a rear window glass sheet fitted to a rear window opening of an automobile. A part of the defogger and a part or the entirety of the antenna conductor are laid one upon another by interposing an insulation layer.
Further, there is provided a glass antenna for an automobile in which an electric heating type defogger having a large number of heater strips and a plurality of bus bars, and an antenna conductor, are provided on a rear window glass sheet fitted to a rear window opening of an automobile. The antenna conductor and at least one heater strip cross each other, and are laid one upon another by interposing an insulation layer in the crossing portion.
By adopting the above-mentioned constructions, the antenna conductor and the defogger achieve excellent capacitive coupling, and received signals in the defogger can be utilized effectively whereby sensitivity can be improved.